I'm trying to use the equation driven curve tool to sketch a catenary y=a*cosh(x/a) but keep getting told that it is an invalid equation. I generated some random data to test P1 (0,0) P2 (0,10) S=15 h=10 v=0 I found a to be 0.7365. Anyone care to tell me why the equation is invaild?

SW doesn't accept hyperbolic functions like cosh in equations or equation driven curves. Try the longer form:

0.5*a*(exp(t/a) + exp(-1*(t/a)))

Jim S.